Gas vent for electrochemical cell

ABSTRACT

An electrochemical cell system is configured to utilize an ionically conductive medium flowing through a plurality of electrochemical cells. One or more gas vents are provided along a flow path for the ionically conductive medium, so as to permit gasses that evolve in the ionically conductive medium during charging or discharging to vent outside the cell system, while constraining the ionically conductive medium within the flow path of the electrochemical cell system.

The present application claims priority to U.S. Provisional ApplicationSer. No. 61/515,749, filed on Aug. 5, 2011, the entirety of which ishereby incorporated by reference.

FIELD

The present invention is generally related to an electrochemical cellsystem, and more particularly to an electrochemical cell systemutilizing a liquid electrolyte.

BACKGROUND

Many types of electrochemical cells utilize a liquid electrolyte tosupport electrochemical reactions within the cell. For example, ametal-air electrochemical cell system may comprise a plurality of cells,each having a fuel electrode serving as an anode at which metal fuel isoxidized, and an air breathing cathode at which gaseous oxygen fromambient air is reduced. Such a cell may also comprise an electrolyte tocommunicate the oxidized/reduced ions between the electrodes. Forexample, see U.S. Patent Publication No. 2009/0284229, incorporated inits entirety herein by reference. In some electrochemical cell systemscomprising a plurality of electrochemical cells, the electrolyte may beshared by multiple cells. For example, the electrolyte may flow inseries from one cell to another, such as is described in U.S. patentapplication Ser. No. 12/631,484, incorporated herein in its entirety byreference. In other electrochemical cell systems, the electrolyte may beshared by multiple cells, but may flow partially in parallel.

In some electrochemical cell systems, various gasses may evolve duringthe charging and/or discharging of the cell. Such gasses may be harmfulto the cell, and may damage or impede performance of the cell. Forexample, in some cases the cell may be harmed due to the evolved gassesincreasing pressure within a confined area in the cell. In some cases,the cell (and potentially its surroundings) may be harmed due to theevolution of a potentially volatile gas or combination of gasses. Someelectrochemical cells are configured to disperse such gasses byincluding vents therein, so that gasses may escape into the ambientenvironment. Other electrochemical cells may be configured with pressurerelief valves, which are typically closed, however open when thepressure within the cell exceeds a threshold amount.

Among other improvements, the present application also endeavors toprovide an effective and improved way of controlling the discharge ofgasses within the cell, without adversely affecting the flow of liquidelectrolytes within the cell and/or the performance of the cell duringoperation.

SUMMARY

According to an embodiment, an electrochemical cell system includes oneor more electrochemical cells, each comprising (i) a fuel electrodecomprising a metal fuel; and (ii) an oxidant electrode spaced from thefuel electrode. The electrochemical cell system also includes a liquidionically conductive medium for conducting ions between the fuel andoxidant electrodes to support electrochemical reactions at the fuel andoxidant electrodes, and a housing configured to contain the ionicallyconductive medium in the one or more electrochemical cells. Theelectrochemical cell system further includes a gas permeable and liquidimpermeable membrane positioned along a portion of the housing andconfigured to close the portion of the housing to contain the ionicallyconductive medium therein but permit gas in the housing to permeatetherethrough for venting of the gas from the one or more electrochemicalcells. The fuel electrode and the oxidant electrode are configured to,during discharge, oxidize the metal fuel at the fuel electrode andreduce an oxidant at the oxidant electrode to generate a dischargepotential difference therebetween for application to a load.

According to another embodiment, a method for assembling anelectrochemical cell system includes providing a cell module configuredto receive a liquid ionically conductive medium therein, and installinga fuel electrode configured to store a metal fuel therein into a cellchamber of the cell module. The method additionally includes providing aplate for the cell module, and installing an oxidant electrode and a gaspermeable and liquid impermeable membrane on the plate. The methodfurther includes joining the plate and the cell module such that theionically conductive medium is prevented from permeating therebetween,and the oxidant electrode is spaced from the fuel electrode. The fuelelectrode and the oxidant electrode are configured to, during discharge,oxidize the metal fuel at the fuel electrode and reduce an oxidant atthe oxidant electrode to generate a discharge potential differencetherebetween for application to a load. Additionally, the gas permeableand liquid impermeable membrane is positioned along a portion of thecell module and configured to close the portion of the cell module tocontain the ionically conductive medium therein but permit gas in thecell module to permeate therethrough for venting of the gas from theelectrochemical cell system.

According to another embodiment, an electrochemical cell system includesa housing and one or more electrochemical cells positioned within thehousing. Each of the one or more electrochemical cells includes (i) afuel electrode comprising a metal fuel; and (ii) an oxidant electrodespaced from the fuel electrode. The electrochemical cell systemadditionally includes a gas permeable and liquid impermeable membranepositioned to define a portion of a surface of the housing, and a liquidionically conductive medium, within the housing, for conducting ionsbetween the fuel and oxidant electrodes to support electrochemicalreactions at the fuel and oxidant electrodes. The fuel electrode and theoxidant electrode are configured to, during discharge, oxidize the metalfuel at the fuel electrode and reduce an oxidant at the oxidantelectrode to generate a discharge potential difference therebetween forapplication to a load. Additionally, the gas permeable and liquidimpermeable membrane is configured to prevent permeation of theionically conductive medium out of the housing, but permit gas in thehousing to permeate therethrough for venting of the gas from the one ormore electrochemical cells.

According to another embodiment, an oxidant electrode and vent assemblyfor an electrochemical cell comprises a gas permeable and liquidimpermeable membrane, and one or more oxidant electrode active materialsprovided on a first portion of the gas permeable and liquid impermeablemembrane, but not a second portion of the gas permeable and liquidimpermeable membrane. When the oxidant electrode and vent assembly ismounted to an electrochemical cell comprising a fuel electrode and aliquid ionically conductive medium such that the liquid ionicallyconductive medium contacts the one or more oxidant electrode activematerials and the fuel electrode, the fuel electrode and the one or moreoxidant electrode active materials are configured to, during discharge,oxidize the metal fuel at the fuel electrode and reduce a gaseousoxidant received through the gas-permeable and liquid impermeablemembrane at the one or more oxidant electrode active materials, togenerate a discharge potential difference therebetween for applicationto a load. Additionally, at least the first portion of the gas permeableand liquid impermeable membrane is configured to prevent permeation ofthe ionically conductive medium out of the electrochemical cell andpermit the gaseous oxidant to permeate into the one or more oxidantelectrode active materials. Furthermore, at least the second portion ofthe gas permeable and liquid impermeable membrane is configured topermit gas in the electrochemical cell to permeate therethrough forventing of the gas from the electrochemical cell, and prevent permeationof the ionically conductive medium out of the electrochemical cell.

Other aspects of the present invention will become apparent from thefollowing detailed description, the accompanying drawings, and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 illustrates side and perspective views of a cell moduleconfigured to house an electrochemical cell, and define a flow path foran ionically conductive medium utilized by the electrochemical cell;

FIG. 2 illustrates perspective and exploded views of a cell assemblyincluding the cell module of FIG. 1, further comprising covering platesconfigured to contain the flow of the ionically conductive medium withinthe cell module of FIG. 1, and to permit air access to one or more aircathodes of the one or more electrochemical cells;

FIG. 3 illustrates an assembly of a plurality of the cell assemblies ofFIG. 3, arranged such that air may reach the one or more air cathodesthrough the covering plates;

FIG. 4 illustrates a side view of the cell module of FIG. 1, with flowmanifolds therein to direct the flow through flow lanes associated withthe one or more electrochemical cells assembled in the housing;

FIG. 5 illustrates a detailed view from FIG. 4, enlarging one of theflow manifolds and depicting the flow lanes connecting thereto within afuel electrode;

FIG. 6 illustrates a cross sectional view of the fuel electrode of FIG.5, showing the flow lanes defined by spacers therein;

FIG. 7 illustrates a cross sectional view of another embodiment of thefuel electrode of FIG. 5, having a stepped scaffold configurationconfigured to be shared by opposing oxidant electrodes;

FIG. 8 illustrates a cross sectional view of an embodiment of anelectrode assembly including the fuel electrode of FIG. 7, furtherincluding separate charging electrodes;

FIG. 9 illustrates a schematic view of an electrode assembly configuredto be housed in the cell module, and an oxidant electrode configured tobe housed in one of the covering plates, electrically connected via aswitching system;

FIG. 10 illustrates an embodiment of the cell assembly of FIG. 2 withthe backside plate cover removed to show the oxidant electrode and theelectrode assembly of FIG. 9 housed therein;

FIG. 11 illustrates another embodiment of the cell assembly of FIG. 2,with where the backside cover contains a gas vent that is integratedinto the oxidant electrode as an oxidant electrode and vent assembly;and

FIG. 12 illustrates a schematic side view of an embodiment of theoxidant electrode and vent assembly of FIG. 18.

DETAILED DESCRIPTION

FIG. 1 illustrates perspective and side views of an electrochemical cellmodule 100, configured to house one or more cells 105 at least partiallyin a cell chamber 110. The cells 105, described in greater detail below,are configured to utilize an ionically conductive medium that flowsthrough or is otherwise contained in and/or constrained by portions ofthe cell module 100, to conduct ions therein. The ionically conductivemedium will also be described in greater detail below. While in someembodiments the ionically conductive medium may be generally stationarywithin the cell module 100, such as in a pool or other quantity ofionically conductive medium, in other embodiments such as thoseillustrated herein, the ionically conductive medium may be configured toflow into, through, and out of the electrochemical cell module 100. Insome embodiments, the ionically conductive medium may be stored in areservoir R (not shown), and a flow pump FP (also not shown) may be usedto pump the ionically conductive medium through one or more cell modules100. In embodiments wherein the ionically conductive medium is flowingthrough the one or more cell modules 100, the rate of flow may vary indifferent embodiments. For example, in some embodiments, a constant flowof ionically conductive medium may be maintained, while in otherembodiments the ionically conductive medium may be pulsed periodicallythrough the cell. In some embodiments, sensors may be associated withthe cell, and may provide signals (including but not limited to anindication of the passage of time, or an indication of a reduction ofcell performance), which may prompt the flow pump FP to flow or pulsethe ionically conductive medium. As illustrated, the cell module 100 mayhave at least one cell inlet 120, configured to permit the ionicallyconductive medium to enter the cell module 100, and at least one celloutlet 130 configured to permit the ionically conductive medium to leavethe cell module 100. More details of the electrochemical cell module 100and each cell 105 will be discussed below.

As the ionically conductive medium is electrically conductive, the flowof ionically conductive medium through multiple cells 105 may causeshunt current, the parasitic or counter-productive current that flowsthrough the ionically conductive medium between electrodes of differentcells 105 housed in adjacent cell modules 100, reducing an overallpotential difference across the cell modules 100. Physical separation ofthe ionically conductive medium may serve to disrupt the shunt current,by breaking the counter-productive electrical connections formed in theionically conductive medium, creating at least some current isolation.To physically separate the ionically conductive medium across multiplecell modules 100, each cell module 100 may include one or more flowdispersers, such as those described in U.S. patent application Ser. No.13/362,775, incorporated herein in its entirety by reference.

In the illustrated embodiment, once the ionically conductive mediumenters cell inlet 120, it flows along inlet channel 140 towards an inletdisperser chamber 150. As shown, inlet channel 140 may travel upwards(i.e. against the force of gravity) so that gravity can assist in thedispersal of the ionically conductive medium in the inlet disperserchamber 150. In the illustrated embodiment, the inlet disperser chamber150 contains a flow disperser 160 configured to break up the flow of theionically conductive medium by passing it through one or more nozzles170. In an embodiment, flow disperser 160 will be positioned at aterminal end of inlet channel 140 so that the ionically conductivemedium will fall downward through the one or more nozzles 170, and, in adispersed form through the remainder of inlet disperser chamber 150. Bydispersing the ionically conductive medium, any electrical current, suchas shunt current, that could otherwise flow through the ionicallyconductive medium would be broken, preventing or minimizing theinfluence of such currents between fluidically connected cell modules100.

In various embodiments, the inlet disperser chamber 150 may vary interms of the shape, size, number, and configuration of the one or morenozzles 170. In some embodiments, the size, shape, and number of nozzles170 in inlet disperser 160 may be determined by a flow rate of theionically conductive medium through the cell housing 100. As shown inthe illustrated embodiment, in some embodiments an air inlet 180 may beprovided to permit a flow of air into inlet disperser chamber 150. Insome embodiments inlet disperser 160 may contain an air nozzle that isconnected to air inlet 180, while in other embodiments air inlet 180 maylead directly into a post-dispersal portion of the inlet disperserchamber 150. In an embodiment, the air inlet 180 may create apressurized amount of air in the inlet disperser chamber 150, such thata pressure head is maintained to drive the ionically conductive mediumthrough the cell module 100, despite the passage through inlet disperserchamber 150. In some embodiments wherein the ionically conductive mediummay have a tendency to foam or bubble after dispersion, such airpressure may also be useful in suppressing such action, so that thefoamed or bubbled ionically conductive medium does not collapse the airpocket formed in the inlet dispersion chamber, creating an electricalconnection through the foam or bubbling when the foamed or bubbledionically conductive medium grows to contact the ionically conductivemedium in the one or more nozzles 170.

Once the ionically conductive medium falls in dispersed form through theinlet disperser chamber 150, it may gather at a bottom of a chamber, andflow into a pre-cell channel 190. As shown, the pre-cell channel 190 maybe configured such that the ionically conductive medium may flow throughthe cell 105 in the cell chamber 110. Again, the cell 105 is describedin greater detail below. In the illustrated embodiment, cell module 100may be configured to divide the flow of the ionically conductive mediuminto a plurality of flow lanes across the electrodes of the cell 105. Inthe illustrated embodiment, a pre-cell manifold 200 may be positioned atthe end of the pre-cell channel 190, and configured to split the flow ofthe ionically conductive medium along the flow lanes, which may beformed in the electrodes of the cell 105, as discussed in greater detailbelow. At the opposite end of the cell chamber 110, a post-cell manifold210 may be positioned to receive the flow from the plurality of flowlanes, and recombine the flows. In the illustrated embodiment, theionically conductive medium flows upward (i.e. against the force ofgravity) across the cell chamber 110, and may be pushed by the pressurehead maintained within the cell module 100.

As is shown in the illustrated embodiment, the recombined flows ofionically conductive medium may flow into a post-cell chamber 220,discussed in greater detail below, which may then lead to a post-cellchannel 230. The post-cell channel 230 may be positioned to allow theionically conductive medium to flow from the post-cell chamber 220,through the post-cell channel 230, and fall under the force of gravitythrough an outlet disperser chamber 240. As shown, outlet disperserchamber 240 may contain an outlet disperser 250, which again may containone or more nozzles 260. In some embodiments, outlet disperser 250 maybe of a similar construction and configuration as inlet disperser 160.In other embodiments, outlet disperser 250 may differ from inletdisperser 160. For example, in embodiments, where the inlet disperser160 contains an air nozzle to connect to air inlet 180, outlet disperser250 may lack such an air nozzle. In some embodiments, this may beacceptable, as the outlet disperser chamber 240 may be connected to thereservoir R via the cell outlet 130, and thus there would be no need tomaintain the pressure head following nozzles 260, nor would theionically conductive medium generally foam, bubble, or otherwise back upwithin the outlet disperser chamber 240. In the illustrated embodiment,ionically conductive medium that is dispersed by outlet disperser 250falls in dispersed form (i.e. discrete droplets) through the remainderof the outlet disperser chamber 240, and flows out the cell outlet 130.

The cell module 100 may be of any suitable structure or composition,including but not limited to being formed from plastic, metal, resin, orcombinations thereof. Accordingly the cell module 100 may be assembledin any manner, including being formed from a plurality of elements,being integrally molded, or so on. In various embodiments the cellmodule 100, the cells 105, and/or appurtenant structures and assembliesmay include elements or arrangements from one or more of U.S. patentapplication Ser. Nos. 12/385,217, 12/385,489, 12/549,617, 12/631,484,12/776,962, 12/885,268, 13/028,496, 13/083,929, 13/167,930, 13/185,658,13/230,549, 13/299,167, 13/531,962, 13/532,374, and 61/556,011, each ofwhich are incorporated herein in their entireties by reference. The flowpath of the ionically conductive medium through the cell module 100 maydiffer in various embodiments, and the illustrated embodiment of FIG. 1is merely exemplary, and is not intended to be limiting in any way.

Shown in FIG. 2 are perspective and exploded views of a cell assembly270. As shown in the exploded view, the cell assembly 270 includes thecell module 100, enclosed by frontside plate 280 and backside plate 290.In an embodiment, the faces of frontside plate 280 and backside plate290 that are configured to be directed towards the cell module 100 maybe shaped and configured to match contours of the cell module 100, so asto assist in forming seals around the flow path defined in the cellmodule 100, and confine the ionically conductive medium to the flow pathof the cell assembly 270. For example, in an embodiment, backside plate290 forms a portion of the flowpath backside wall. As shown in theillustrated embodiment, backside plate 290 includes pre-cell manifoldbackwall 300, which would back onto pre-cell manifold 200 of the cellmodule 100, to partially enclose the flow path through the pre-cellmanifold 200. A corresponding pre-cell manifold frontwall (not shown)would correspondingly be positioned on the frontside plate 280, suchthat the ionically conductive medium would be prevented from flowing outeither the front or back faces of the pre-cell manifold 200, but insteadwould flow through the cell assembly 270 from the pre-cell channel 190to the cell chamber 110.

In embodiments where frontside plate 280 and backside plate 290 areshaped to enclose the entirety of the flow path in cell module 100, thefront and back faces of cell chamber 110, inlet disperser chamber 150,outlet disperser chamber 240, and the interconnecting portions of theflow path to and from these elements would all be sealed by frontsideplate 280 and backside plate 290. In other embodiments, however,frontside plate 280 and backside plate 290 may be configured to encloseless than the entirety of the flow path in cell module 100. For example,in the embodiment illustrated in FIG. 2, while the frontside plate 280is sized to enclose the entire front side of cell module 100, includingthe front faces of cell chamber 110, inlet disperser chamber 150 outletdisperser chamber 240, and the interconnecting flow path, the backsideplate 290 is shown to be smaller. As shown, instead of backside plate290 enclosing the backside of inlet disperser chamber 150, the backsideof outlet disperser chamber 240, or the backsides of some of theassociated portions of the flow path surrounding them, the backside ofcell module 100 provides the back side of these elements. This maycreate a U-shaped or open-box cross section for the inlet disperserchamber 150, the outlet disperser chamber 240, and the backsides ofassociated portions of the flow path surrounding them. In such anembodiment, the securing of frontside plate 280 to cell module 100 wouldenclose the flow path in at least these areas (i.e. closing the openside of U-shape on the cross section) permitting a smaller backsideplate 290. The smaller backside plate 290 could be shaped to encloseonly those areas where access to the back face of cell module 100 wouldbe desirable. For example, it may be desirable to access the back faceof cell chamber 110, so as to provide access to the opposing side of thecell 105. Such a configuration may be useful, for example, where thereare two cells 105 located within cell chamber 110, or where a singlefuel electrode is shared by a pair of opposing oxidant electrodes, asdiscussed in greater detail below.

In some embodiments, a sealing material may be applied between the cellmodule 100 and the frontside plate 280 and/or the backside plate 290, toensure liquid impermeability and prevent leakage. In variousembodiments, the sealing material for the frontside plate 280 andbackside plate 290 may comprise or include plastic or rubber gaskets,adhesives, or other sealants, including but not limited to solvent-bondsealants, single or two-part (i.e. base and accelerator) epoxies, orUV/thermally cured epoxies. In various embodiments, the sealants maycomprise ABS glue weld-on 4707, MEK (methyl ethyl ketone), or havesealant properties similar to those marketed as Eager Polymer EP5347epoxy and/or MagnaTac M777 epoxy, to prevent the undesirable loss ofionically conductive medium or flow pressure at the site where theseelements join. In an embodiment, the sealing material may benon-conductive and electrochemically inert, to prevent interference withthe electrochemical reactions of the cell 105.

As is further shown in the illustrated embodiment, the backside plate290 may include a post-cell chamber backwall space 310, which maycoordinate with a corresponding post-cell chamber frontwall space (notshown) on frontside plate 280, to define boundaries for post-cellchamber 220, as discussed below. Backside plate 290 may additionallyinclude a backwall 320 configured to close the backside of cell chamber110 of cell module 100. In the illustrated embodiment, backside plate290 may be configured to receive an oxidant electrode, mounted to lip330, to provide an oxidizer for electrochemical reactions in the cell105. The oxidant electrode may be liquid impermeable, and thus wouldfluidly seal the ionically conductive medium to the flow path from thebackside of cell chamber 110. Frontside plate 280 may include a similarstructure to surround the frontside of cell chamber 110. The lip 330, incooperation with a plurality of air apertures 340, and associated airchannels 350 on each of frontside plate 280 and backside plate 290permit a spacing between the oxidant electrode mounted to the lip 330,such that air may flow into the aperture 340 to provide oxygen from theair to the oxidant electrode. The air channels 350 may be recessed intothe frontside plate 280 and the backside plate 290, as shown, such thatwhen a plurality of cell assemblies 270 are aligned together, as shownin FIG. 3, the combined air channels 350 permit the flow of air betweeneach pair of cell assemblies 270.

Although in some embodiments the oxidizer may be delivered to theoxidant electrode by a passive system (such as through the air channels350), which may be sufficient to allow diffusion or permeation of oxygenfrom the air into the oxidant electrode, in other embodiments differentsources of the oxidizer or mechanisms for bringing the oxidizer to theoxidant electrode may be utilized. For example, in an embodiment, a pumpsuch as an air pump AP may be used to deliver the oxidizer to theoxidant electrode under pressure. The air pump AP may be of any suitableconstruction or configuration, including but not limited to being a fanor other air movement device configured to produce a constant or pulsedflow of air or other oxidant. The oxidizer source may be a containedsource of oxidizer. In an embodiment, oxygen may be recycled from theelectrochemical cell module 100, such as is disclosed in U.S. patentapplication Ser. No. 12/549,617, incorporated in its entirety above byreference. Likewise, when the oxidizer is gaseous oxygen from ambientair, the oxidizer source may be broadly regarded as the deliverymechanism, whether it is passive or active (e.g., pumps, blowers, etc.),by which the air is permitted to flow to the oxidant electrode. Thus,the term “oxidizer source” is intended to encompass both containedoxidizers and/or arrangements for passively or actively deliveringoxygen from ambient air to the oxidant electrode.

As may further be appreciated from FIG. 3, in some embodiments where thecell inlet 120 and the cell outlet 130 are proximal to one another ineach of the cell modules 100, a number of configurations for the flow ofthe ionically conductive medium may be easily permitted. For example, insome embodiments, all of the cell inlets 120 may be coupled together bya manifold, and all of the cell outlets 130 may be coupled together by amanifold, such that the ionically conductive medium flows through thecell assemblies 270 in parallel. In another embodiment, the intermediatecell outlets 130 may be coupled to the adjacent cell inlet 120, suchthat the ionically conductive medium flows through all cell assemblies270 in series. Also as shown, each of the air inlets 180 may be adjacentto one another when the cell assemblies 270 are aligned, which may easethe coupling of air inlet tubing for such embodiments. In variousembodiments, an air inlet manifold may couple all air inlets 180 to asingle tube that is coupled to an air pump AP, while in otherembodiments separate tubes may all couple to one or more air pumps AP.

Turning to FIGS. 4-7, the assembly and operation of an embodiment of theelectrochemical cells 105 may be appreciated. As shown in FIG. 4, thecell 105 held by cell module 100 may include a fuel electrode 360positioned in cell chamber 110 so that it is supported by the cellchamber 110 and a plurality of spacers 370 that create flow lanes 380 inthe fuel electrode 360. In an embodiment, the fuel electrode 360 is ametal fuel electrode that functions as an anode when the cell 105operates in discharge, or electricity generating, mode, as discussed infurther detail below. In an embodiment, the fuel electrode 360 maycomprise a plurality of permeable electrode bodies 360 a-360 f, asillustrated in FIG. 6. Each electrode body may include a screen that ismade of any formation that is able to capture and retain, throughelectrodepositing, or otherwise, particles or ions of metal fuel fromthe ionically conductive medium that flows through the cell module 100.

The plurality of spacers 370, each of which extends across the fuelelectrode 360 in a spaced relation to each other, may be connected tothe cell chamber 110 so that the fuel electrode 360 may be held in placerelative to the cell chamber 110 and to the oxidant electrode (not shownin FIGS. 4-7). The permeable electrode bodies 360 a-360 f, asillustrated in FIG. 6, may be separated by sets of the plurality ofspacers 370, so that each set of spacers 370 is positioned in betweenadjacent electrode bodies to electrically isolate the electrode bodies360 a-360 f from each other. Within each set of spacers 370 betweenadjacent electrode bodies, the spacers 370 are positioned in a spacedrelation in a manner that creates the so-called “flow lanes” 380therebetween. The spacers 370 are non-conductive and electrochemicallyinert so they are inactive with regard to the electrochemical reactionsin the cell 105. The spacers 370 may be made from a suitable plasticmaterial, such as polypropylene, polyethylene, polyester, noryl, ABS,fluoropolymer, epoxy, or so on. The flow lanes 380 are three-dimensionaland have a height that is substantially equal to the height of thespacers 370, as illustrated in FIG. 6.

In the illustrated embodiment, the cell chamber 110 has a generallysquare shape that substantially matches the shape of the fuel electrode360. One side or end of the cell chamber 110 is connected to thepost-disperser channel 190 by the pre-cell manifold 200, which dividethe flow of the ionically conductive medium into a plurality of flowsthrough the cell chamber inlets 390. Each cell chamber inlet 390 issubstantially aligned with a corresponding flow lane 380, as illustratedin FIG. 5. After the ionically conductive medium has flowed through theflow lanes 380, the ionically conductive medium may exit the cellchamber 110 through the post-cell manifold 210, which has a plurality ofcell chamber outlets 400, which are illustrated in FIG. 4.

The permeable bodies 360 a-360 f and the spacers 370 may be formed as asingle unit prior to the first electrode 360 being placed in the cellchamber 110. In other words, the fuel electrode 360 illustrated in FIG.6 may be formed as a single unit using any suitable manufacturingprocess. For example, in an embodiment, manufacturing spacers (notshown) that are substantially the size of the desired flow lanes 380 maybe placed between adjacent permeable bodies 360 a-360 f to hold theadjacent permeable electrode bodies 360 a-360 f in a substantiallyparallel spaced relation. The manufacturing spacers that are locatedbetween the same adjacent permeable electrode bodies are preferablysubstantially parallel to each other and equally spaced along theelectrode bodies 360 a-360 f, and the manufacturing spacers that arelocated on opposite sides of the same electrode body are preferablysubstantially aligned with each other. After the electrode bodies 360a-360 f and manufacturing spacers are in place and held together by anysuitable means, a suitable material to be used for the spacers 370 maybe injected in between the manufacturing spacers and through thepermeable electrode bodies 360 a-360 f. After the material hardens orcures, the manufacturing spacers may be removed from the fuel electrode360 to create the single electrode scaffold unit 360 illustrated in FIG.6.

In an embodiment, an injection mold may be fabricated such that themanufacturing spacers are part of the mold. Slots may be formed in themold to accommodate the permeable electrode bodies 360 a-360 f, andcavities defining the volumes for the spacers 370 may also be formed.Each of the electrode bodies 360 a-360 f may be inserted into the moldin a parallel spaced relation to an adjacent body, and the material tobe used for the spacers 370 may then be injected into the cavities toform the spacers 370. After the material has cooled in the mold, thefirst electrode 360 may be ejected from the mold as a single unitcontaining the permeable electrode bodies 360 a-360 f and the spacers370. Of course, any suitable manufacturing method that allows thespacers 370 to be integrally formed on and through the permeableelectrode bodies 360 a-360 f so that the fuel electrode 360 comprisingthe electrode bodies 360 a-360 f and the spacers are a single unit maybe used. The above-described methods are not intended to be limiting inany way.

In some embodiments, the permeable electrode bodies 360 a-360 f may havesubstantially the same size. In an embodiment, the permeable electrodebodies 360 a-360 f may have different sizes so that a stepped scaffoldconfiguration may be used, as described by U.S. patent application Ser.No. 13/167,930, incorporated above in its entirety by reference. In anembodiment, a pair of fuel electrodes 360 may be positioned within cellmodule 105, one associated with frontside plate 280, the other withbackside plate 290, each having their own associated oxidant electrodeto create a pair of cells 105 housed within cell module 100. In anembodiment, an inert material may be placed between a pair of fuelelectrodes 360 to fully separate the pair of cells 105. In anotherembodiment, such as that shown in FIG. 7, a double-sized fuel electrode360′ may be configured to be positioned in the center of cell chamber110, and associated with both oxidant electrodes, creating a pair ofcells 105 with a common fuel electrode 360, within the cell module 100.As shown, fuel electrode 360′ is configured to share a terminalelectrode body 360 a, while having multiples of electrode bodies 360 b-fspaced in opposite directions therefrom by the spacers 370. Also asshown, the embodiment of fuel electrode 360′ in FIG. 7 may utilize astepped scaffold configuration similar to that described in patentapplication Ser. No. 13/167,930. Shown in FIG. 8 is an embodiment of anelectrode assembly 410 that is formed by the combination of fuelelectrode 360′ and separate charging electrodes 420 spaced fromelectrode bodies 360 f, distal from terminal electrode body 360 a. Theseparate charging electrode 420 will be described in greater detailbelow. In embodiments of fuel electrode 360 designed to be associatedwith a single oxidant electrode, the separate charging electrode 420 maysimply be the electrode body that is proximal to the oxidant electrode.In other embodiments, there might not be a “separate” charging electrodesuch as separate charging electrode 420, and the oxidant electrode maybe utilized both during charging and discharging of the cell 105 (i.e.as an anode during charging and as a cathode during discharging). Insome embodiments, the separate charging electrode 420 may extend atleast as far as the longest of the permeable electrode bodies 360 a-f,when those electrode bodies 360 a-f are in a stepped scaffoldconfiguration, or otherwise vary in size.

Shown in FIG. 9 is a schematic view of an embodiment of the cell 105.The embodiment of the cell 105 described herein is by way of exampleonly, and is not intended to be limiting in any way. In the embodiment,the cell 105 includes the electrode assembly 410 housed in the cellmodule 100 (i.e. in the cell chamber 110), and an oxidant electrode 430.As shown, the oxidant electrode 430 is housed in the backside plate 290.In other embodiments the oxidant electrode 430 may be housed in thefrontside plate 280, as described above, or both, associated withseparate cells 105. As shown, the electrode assembly 410 includes thefuel electrode 360 and a separate charging electrode 420. The fuelelectrode 360 of the illustrated embodiment includes one or more of theelectrode bodies 360 a-e. In an embodiment, the electrode bodies 360 a-emay be screens that are made of any formation able to capture andretain, through electrodepositing, or otherwise, particles or ions ofmetal fuel from the ionically conductive medium that circulates throughthe cells 105 of the cell assembly 270, as discussed above. Componentsof the cell 105, including for example, the fuel electrode 360, thepermeable electrode bodies 360 a-e thereof, the separate chargingelectrode 420, and the oxidant electrode 430, may be of any suitableconstruction or configuration, including but not limited to beingconstructed of Nickel or Nickel alloys (including Nickel-Cobalt,Nickel-Iron, Nickel-Copper (i.e. Monel), or superalloys), Copper orCopper alloys, brass, bronze, or any other suitable metal. In anembodiment, a catalyst film may be applied to some or all of thepermeable electrode bodies 360 a-e, the separate charging electrode 420and/or the oxidant electrode 430, and have a high surface material thatmay be made of some of the materials described above. In an embodiment,the catalyst film may be formed by techniques such as thermal spray,plasma spray, electrodeposition, or any other particle coating method.

The fuel may be a metal, such as iron, zinc, aluminum, magnesium, orlithium. By metal, this term is meant to encompass all elements regardedas metals on the periodic table, including but not limited to alkalimetals, alkaline earth metals, lanthanides, actinides, and transitionmetals, post-transition metals including metalloids, either in atomic,molecular (including metal hydrides), or alloy form when collected onthe electrode body. However, the present invention is not intended to belimited to any specific fuel, and others may be used. The fuel may beprovided to the cell 105 as particles suspended in the ionicallyconductive medium. In some embodiments, a metal hydride fuel may beutilized in cell 105.

The ionically conductive medium may be an aqueous solution. Examples ofsuitable mediums include aqueous solutions comprising sulfuric acid,phosphoric acid, triflic acid, nitric acid, potassium hydroxide, sodiumhydroxide, sodium chloride, potassium nitrate, or lithium chloride. Themedium may also use a non-aqueous solvent or an ionic liquid. In thenon-limiting embodiment described herein, the medium is aqueouspotassium hydroxide. In an embodiment, the ionically conductive mediummay comprise an electrolyte. For example, a conventional liquid orsemi-solid electrolyte solution may be used, or a room temperature ionicliquid may be used, as mentioned in U.S. patent application Ser. No.12/776,962, the entirety of which is incorporated above by reference. Inan embodiment where the electrolyte is semi-solid, porous solid stateelectrolyte films (i.e. in a loose structure) may be utilized.

The fuel may be oxidized at the fuel electrode 360 when the fuelelectrode 360 is operating as an anode, and an oxidizer, such as oxygen,may be reduced at the oxidant electrode 430 when the oxidant electrode430 is operating as a cathode, which is when the cell 105 is connectedto a load L and the cell 105 is in discharge or electricity generationmode, as discussed in further detail below. The reactions that occurduring discharge mode may generate by-product precipitates, e.g., areducible fuel species, in the ionically conductive medium. For example,in embodiments where the fuel is zinc, zinc oxide may be generated as aby-product precipitate/reducible fuel species. The oxidized zinc orother metal may also be supported by, oxidized with or solvated in theelectrolyte solution, without forming a precipitate (e.g. zincate may bea dissolved reducible fuel species remaining in the fuel). During arecharge mode, which is discussed in further detail below, the reduciblefuel species, e.g., zinc oxide, may be reversibly reduced and depositedas the fuel, e.g., zinc, onto at least a portion of the fuel electrode360 that functions as a cathode during recharge mode. During rechargemode, either the oxidant electrode 430 or the separate chargingelectrode 420, and/or another portion of the fuel electrode 360, asdescribed below, functions as the anode.

FIG. 9 shows that the permeable electrode bodies 360 a-e, the separatecharging electrode 420, and the oxidant electrode 430 may be connectedby a switching system 440 that may be configured to connect the cell 105to a power supply PS, a load L, or other cells 105 in series. Suchconnections may be made through a first terminal 450 and a secondterminal 460, wherein the first terminal 450 is negative (cathodic)during charging, and the second terminal 460 is positive (anodic) duringrecharging. During discharge, the fuel electrode 360 is connected to theload L, and operates as an anode so that electrons given off by themetal fuel, as the fuel is oxidized at the fuel electrode 360, flows tothe external load L. The oxidant electrode 430 functions as the cathodeduring discharge, and is configured to receive electrons from theexternal load L and reduce an oxidizer that contacts the oxidantelectrode 430, specifically oxygen in the air surrounding the cellassembly 270.

The operation of the switching system 440 may vary across embodiments,and in some embodiments the operation of the switching system 440 may besimilar to those described in U.S. patent application Ser. No.13/299,167, incorporated in its entirety by reference above. As anotherexample, in an embodiment, the external load L may be coupled to each ofthe permeable electrode bodies 360 a-360 e in parallel, as described indetail in U.S. patent application Ser. No. 12/385,489, filed on Apr. 9,2009 and incorporated above by reference in its entirety. In otherembodiments, the external load L may only be coupled to a terminal oneof the permeable electrode bodies 360 a-360 e (i.e. the electrode body360 a, distal from the oxidant electrode 430), so that fuel consumptionmay occur in series from between each of the permeable electrode bodies360 a-360 e.

In the illustrated embodiment of FIG. 9, the switching system 440includes a bypass switch 470, a charging electrode switch 480, and anoxidant electrode switch 490. The bypass switch 470 is configured toelectrically connect the first terminal 450 to the second terminal 460,bypassing the cell 105 for any number of reasons, including but notlimited to staggering usage of a plurality of the cells 105, isolatingdefective cells 105, or so on. The oxidant electrode switch 490 allowsconnection of the oxidant electrode 430 to the second terminal 460 tocreate a potential difference between the fuel electrode 360 and theoxidant electrode 430 during discharge of the cell 105. The chargingelectrode switch 480 is configured to connect at least the chargingelectrode 420, and potentially some of the fuel electrode 360 (asdescribed in greater detail below) to the second terminal 460, so as tocreate a potential difference with the remainder of the fuel electrode360, connected to first terminal 450.

In some non-limiting embodiments, the switches of switching system 440may be single pole single throw or single pole double throw. They may beof the pivoting, sliding or latching relay type. Also, semiconductorbased switches may be used as well. The switches may be activatedelectrically (electromechanical relay) or magnetically or by othermethods known to those familiar in the art. Any other suitable types ofswitch and switch configurations may be used, and the examples hereinare not limiting. In an embodiment, the plurality of switches may beconnected in series if the switch has a leakage current in onedirection. For example, the body diode of a MOSFET semiconductor basedswitch will conduct in one direction and the leakage current can beeliminated by placing MOSFET semiconductor based switches facing back toback in series.

As is shown in the illustrated embodiment, a plurality of electrode bodyswitches 500 b-e are configured to alternatively connect each ofelectrode bodies 360 b-e to either a first bus 510 a associated withelectrode body 360 a (and thus first terminal 450), or a second bus 510b associated with the separate charging electrode 420 (and thus secondterminal 460 through charging electrode switch 480). In an embodiment,electrode body switches 500 b-e may be characterized as Single Pole,Double Throw. In some embodiments, electrode body switches 500 b-e mayhave three alternative settings, such that each electrode body 360 b-emay be electrically connected to electrode body 360 a (and firstterminal 450), separate charging electrode 420, or disconnected fromboth electrode body 360 a and separate charging electrode 420. In anembodiment, such electrode body switches 500 b-e may be characterized asSingle Pole, Triple Throw. As shown, by connecting each of electrodebodies 360 b-e to either the first bus 510 a or the second bus 510 b,each of the permeable electrode bodies 360 b-e may either be part of thefuel electrode, or the charging electrode, by being electricallyconnected to the first terminal 450 or the second terminal 460respectively.

As shown in the illustrated embodiment, the switches of the switchingsystem 440 may be controlled by a controller 520, which may be of anysuitable construction and configuration. In an embodiment, thecontroller 520 may be configured to manage application of the anodicpotential from the power supply PS to permeable electrode bodies 360 b-3and the charging electrode 420. The controller 520 may causeelectrodeposition of metal fuel, through reduction of reducible ions ofthe metal fuel from the ionically conductive medium, to progressivelygrow from permeable electrode body 360 a to each subsequent electrodebody 360 b-e for application of a cathodic potential to eachsubsequently connected electrode body 360 b-d. The controller 520 mayalso cause removal of the anodic potential from each subsequentlyconnected electrode body, and may cause application of the anodicpotential to at least the subsequent electrode body unconnected by theelectrodeposition, or the charging electrode 420 where the lastelectrode body (i.e. electrode body 360 e) has been electricallyconnected by the electrodeposition to the prior electrode bodies 360a-d. Such application of the anodic potential may be configured topermit or cause oxidization of an oxidizable species of the oxidant.

In an embodiment, the controller 520 may comprise circuitry configuredto manipulate the switches of switching system 440 based on an input 530to determine the proper switch configuration. In some embodiments, theinput 530 may be instructions to control the controller 520, externalreadings or measurements regarding the cell 105 that may influence theoperation of the switching system 440, or so on. The controller 520 mayalso include a microprocessor for executing more complex decisions, asan option. In some embodiments, the controller 520 may also function tomanage connectivity between the load L and the power source PS and thefirst and Nth cells. In some embodiments, the controller 520 may includeappropriate logic or circuitry for actuating the appropriate bypassswitches 470 in response to detecting a voltage reaching a predeterminedthreshold (such as drop below a predetermined threshold).

In some embodiments, the controller 520 may further comprise or beassociated with a sensing device 540, including but not limited to avoltmeter (digital or analog) or potentiometer or other voltagemeasuring device or devices, that can be used to determine when tomodify the configuration of the plurality of switches, such as tomaintain the proximity of the anode and the cathode as fuel growthprogresses during charging. In some embodiments, the sensing device 540may instead measure current, resistance, or any other electrical orphysical property across or of the cell 105 that may be used todetermine when to modify the configuration of the plurality of switches.For example, the sensing device 540 may measure a spike in current or adrop in potential difference between two electrode bodies. In someembodiments, the controller 520 may control the switches of theswitching system 440 based on the passage of increments of time. Forexample, in an embodiment the time for fuel growth to progress betweenadjacent electrode bodies may be known, and used to calculate when tooperate the switching system 440 so as to progressively rewire theelectrodes to maintain an adjacent separation between the anode and thecathode, or provide for parallel versus progressive charging, as isdescribed in greater detail in U.S. patent application Ser. Nos.13/230,549 and 13/299,167, incorporated above by reference in theirentireties. In an embodiment, the controller 520 may control theswitches of switching system 440 to provide a high efficiency mode forthe cell, such as is disclosed in U.S. patent application Ser. No.13/083,929, incorporated in its entirety above by reference.

In an embodiment, the controller 520 may be configured to control thebypass switch 470 to bypass the cell 105. In various embodiments, thebypass switch 470 may be closed for any number of reasons, includingbased on readings regarding the cell made by sensing device 540, orbased on external commands fed into the controller 520 via the input530. In an embodiment, the controller 520 may coordinate with othercontrollers 520 associated with other cells 105, and mayprogrammatically control the other controllers 520 to network control ofthe cells 105. In an embodiment, a master controller may be provided tocontrol a plurality of the controllers 520, providing the ability tocontrol the operation of the switching system 440 for a plurality ofcells 105. In an embodiment, the controller 520 may implement analgorithm, such as but not limited to one similar to those disclosed inU.S. patent application Ser. No. 13/299,167, or implement other computeror programmatic control for the switching system 440.

As indicated above, in an embodiment the oxidant electrode 430 may beassembled into and supported by the frontside plate 280 and/or thebackside plate 290. FIG. 10 depicts the rear side of the cell module 100housing the electrode assembly 410 of a cell 105 in the cell chamber110. The electrode assembly 410 may be positioned such that the separatecharging electrode 420 is spaced proximal to the side of cell module 100that will couple with the backside plate 290. In an embodiment, anotherelectrode assembly associated with the frontside plate 280 may bepositioned on the obscured side of cell module 100. The backside plate290, which is configured to be received by the cell module 100, containsthe oxidant electrode 430 therein, which would form the sidewall of thecell chamber 110, and may form a seal or may otherwise be sealed betweenthe cell chamber 110 and the backside plate 290, so that the ionicallyconductive medium flowing through the cell module 100 is confined as itflows through the cell chamber 110.

The oxidant electrode 430 may therefore be liquid impermeable, yet airpermeable, such that air may enter the cell 105 to serve as the oxidantduring the electrochemical reactions taking place during discharge ofthe cell 105, between the oxidant electrode 430 and the fuel electrode360. In an embodiment, the oxidant enters the cell 105 by reaching theoxidant electrode 430 through the air apertures 340 in the backwall 320described above, which are obscured by the oxidant electrode 430 in FIG.10. In an embodiment, the oxidant electrode 430 may be glued into thebackside plate 290 such that a vent layer remains between the backwall320 and the oxidant electrode 430. In an embodiment, the oxidantelectrode 430 may be a metal-air breathing cathode. In an embodiment,oxidant electrode 430 may comprise a catalyst, a current collector, anda hydrophobic membrane. In an embodiment, those elements of the oxidantelectrode 430 that provide for oxygen reduction in the electrochemicalcell 105, including the electrode meshes or coatings used to create apotential difference between the fuel electrode 360 and the oxidantelectrode 430 when the cell 105 is connected to the load L, may becharacterized as the “active material(s)” of the oxidant electrode 430.In some embodiments, the oxidant electrode 430 may be formed by amixture of catalyst particles or materials, conductive matrix andhydrophobic materials sintered to form a composite material or otherwiselayered together. In an embodiment, the surface of the oxidant electrode430 exposed to the ionically conductive medium may be more hydrophiliccompared to the surface exposed to an oxidizer.

It may be appreciated that during the charging and/or the discharging ofthe cell 105, gasses may be evolved during the electrochemicalreactions. For example, during charging of the cell 105, where theionically conductive medium contains reducible zinc ions that are to beplated as zinc fuel on the fuel electrode 360, the electrochemicalreactions occurring are reduction-oxidation (redox) reactions. Thereduction reaction takes place at the fuel electrode 360 (the reductionsite), and may conform to ZnO+H₂O+2e⁻→Zn+2OH⁻. The correspondingoxidation reaction occurs at the charging electrode (i.e. the separatecharging electrode 420), and may conform to 2OH⁻→2e⁻+½O₂+H₂O. Thecharging electrode (which may be characterized as an oxygen evolvingelectrode) is therefore understood to be producing oxygen gas within thecell 105. The local site of the evolution of the oxygen in the cell 105may vary, depending on which of the electrode bodies 360 b-e areassociated with the terminal electrode body 360 a, and which areassociated with the separate charging electrode 420, based on theconfiguration of the switching system 440. In other embodiments, such aswhere different metal fuels are utilized, other reactions may occur,which may also evolve oxygen in the cell.

In some embodiments hydrogen may evolve within the cell 105, orelsewhere in the cell module 100. For example, in some embodiments, thecell module 100 may utilize catch trays, such as those described in U.S.patent application Ser. No. 13/185,658, which may be strategicallypositioned to receive particles of zinc that may separate from the fuelelectrode 360. For example, such catch trays may be positioned near orin the pre-cell manifold 200, so that dendrites or other elements offuel growth that break away from the fuel electrode 360 fall downwardsagainst the flow, and contact the catch tray. In some embodiments, thecatch tray may comprise a catalyst configured to oxidize the fuellocally at the catch tray, so that the separated fuel particles do notclog up or otherwise impede cell performance or the flow of theionically conductive medium. For example, where the metal fuel is zinc,the oxidation may correspond to the equation Zn→Zn²⁺+2e⁻. The zinc ionsmay bond with hydroxide ions that are found in the ionically conductivemedium from the other electrochemical processes in the cell, such thatZn²⁺+4(OH⁻)→Zn(OH)₄ ²⁻, which would flow in the ionically conductivemedium, and be free to be reduced as zinc fuel at the fuel electrode 360during a future charging of the cell 105. The free electrons from theoxidation of the zinc, however, may combine with hydrogen ions in theionically conductive medium from other electrochemical reactions in thecell, such that H⁺+2e⁻→H₂, evolving hydrogen gas within the cell.Although such hydrogen gas would generally be in a much smaller quantitythan the evolved oxygen, it too may be present within the cell module100.

In some embodiments, air intended to remain inside the inlet disperserchamber 150 (i.e. that is let into the cell module 100 by air inlet 180)may migrate out of the disperser chamber 150, into the cell chamber 110.The presence of gasses such as the air from the disperser chamber 150,evolved oxygen and hydrogen from various electrochemical reactionswithin the cell 105 or the catch tray, or any other gas that enters intoor is generated within the cell module 100 may impede the performance ofthe cell 105, and/or the flow of the ionically conductive medium in theflow path. Depending on the nature of the gas or combination of gasses,potentially volatile mixes may arise, which may be harmful to the cellassembly 270, the overall system, or the surrounding environment.

As depicted in the embodiment of FIG. 10, the post-cell chamber backwallspace 310 that is located on the backside plate 290 may comprise a gasvent 550 configured to permit the release of gasses (including but notlimited to those described above) from the cell module 100. The gas vent550 may be of any suitable construction or configuration that is capableof releasing the gasses within the cell module 100 while constrainingthe ionically conductive medium within the flow path by preventingpermeation of the ionically conductive medium therethrough. In otherwords, the gas vent 550 may be air permeable, but liquid impermeable.For example, in an embodiment the gas vent 550 may be a hydrophobicmembrane that is sealed to one or more apertures within the post-cellchamber backwall space 310. In an embodiment, the gas vent 550 may besealed to a portion of the backside plate 290, so that the entirety ofthe post-cell chamber backwall space 310 is the gas vent 550. In variousembodiments, the gas vent 550 may be glued, fused, or otherwise moldedonto or into the post-cell chamber backwall space 310 or the backsideplate 290. In an embodiment, the aperture or apertures in the post-cellchamber backwall space 310 contacting the gas vent 550, or the gas vent550 on the backside plate 290 itself, may lead to the air channels 350,such that the gasses may diffuse with the outside air. In someembodiments, the air channels 350 may extend from the top to the bottomof backside plate 290, or may otherwise continue past the air apertures340 in the backwall 320, so that gasses which vent outside the cellassembly 270 may disperse in the surrounding environment of the cellassembly 270 by either rising or falling depending on the buoyancy ofthe gas as compared to the surrounding air.

In an embodiment, the gas vent 550 may comprise polytetrafluoroethylene(also known as PTFE, or Teflon®), which may in some embodiments bethermo-mechanically expanded (also known as ePTFE, or Gore-Text®). Insome embodiments, the gas vent 550 may further comprise one or morere-enforcing layers configured to provide structural support oradditional protection for the PTFE material. In an embodiment, thereinforcing layers may be configured to prevent excessive deformation ofthe PTFE from the fluid pressure of the ionically conductive medium. Forexample, in some embodiments the reinforcing layer may include acomposite material formed by pressurization and sintering of a mixtureof hydrophobic material (such as PTFE), particles with high mechanicalstrength (such as carbon), and/or other appropriate binders.

In some embodiments, the gas vent 550 may be formed from or otherwiseinclude other fluoropolymer materials. In an embodiment, the gas vent550 may comprise polyurethane. In other embodiments, the gas vent 550may comprise or be formed of other materials having hydrophobicproperties. For example, in some embodiments, the gas vent 550 maycomprise a fabric coated with a durable water repellant, or otherrepellant coating to repel the ionically conductive medium. In variousembodiments, the gas vent 550 may comprise a porous material, whereineach of the pores are significantly smaller than the size of a dropletof the ionically conductive medium, to make the fabric liquidimpermeable. In an embodiment, the gas vent 550 may be of sufficientstrength to contain the ionically conductive medium within the flow pathor other area within the housing or electrochemical cell, and maintainthe pressure head such that the ionically conductive medium continues toflow, without rupturing the gas vent 550, or otherwise losing the flowpressure.

Depicted in FIG. 11 is an embodiment of cell module 100, which may beconfigured to engage another embodiment of the backside plate 290(depicted as backside plate 290′). As shown, backside plate 290′ may beconfigured to include an extended lip 330′, so as to correspond to anarea of cell module 100 that generally includes both cell chamber 110and post-cell chamber 220, wherein a combined gas vent with oxidantelectrode assembly 560, that is generally air-permeable but liquidimpermeable, may be sealed to the extended lip 330′ to facilitateair-permeability into and/or out of the cell chamber 110 and thepost-cell chamber 220, while generally preventing loss of the ionicallyconductive medium therethrough. As shown in FIG. 11, a dividing line 570on the combined gas vent with oxidant electrode assembly 560 may beutilized to demarcate the oxidant electrode 430 from the gas vent 550.In various embodiments, the dividing line 570 may correspond to alocation that would be aligned between the cell chamber 110 and thepost-cell chamber 220 when the backside plate 290′ is assembled onto thecell module 100. For example, in an embodiment, the dividing line 570may generally align to the top of the electrode assembly 410, near thebottom of the post-cell manifold 210. In other embodiments, the dividingline 570 may generally align to the top of the post-cell manifold 210,near the bottom of the post-cell chamber 220. Regardless of the actualdemarcation between the gas vent 550 and the oxidant electrode 430 onthe combined gas vent with oxidant electrode assembly 560, in someembodiments the gas vent 550 may generally align to the post-cellchamber 220, while the oxidant electrode 430 may generally align to theelectrode assembly 410 in the cell chamber 110. In some embodiments,sealants, including but not limited to those described above, may bepositioned across the dividing line 570, which may further assist inflowing the ionically conductive medium through the post-cell manifold210, as described above.

Shown in FIG. 12 is a non-limiting schematic cross-sectional view of aportion of the combined gas vent with oxidant electrode assembly 560depicted above, near the dividing line 570. As shown, in an embodiment,the gas vent 550 and the oxidant electrode 430 may both include a sharedpiece of air-permeable but liquid impermeable material 580, which insome embodiments may comprise materials similar to those described asbeing used for gas vent 550 above. As shown, the portion of theair-permeable but liquid-impermeable material 580 that is associatedwith the oxidant electrode 430 is utilized as a backing material tosupport the active materials that are used to create the potentialdifference with the fuel electrode 360 when the cell 105 is connected tothe load L, while the portion of the air-permeable but liquidimpermeable material 580 that is associated with the gas vent 550 lacksthose active materials.

As an example, in the illustrated embodiment, a conductive layer 590 anda catalyzed active layer 600 are provided on the portion of theair-permeable but liquid-impermeable material 580 that is associatedwith the oxidant electrode 430, and may form layers thereon, asgenerally illustrated. In other embodiments, the conductive layer 590and the catalyzed active layer 600 may be sintered into or otherwisecombined with each other and/or the air-permeable but liquid-impermeablematerial 580. As such, although described and illustrated as layers inthe grossly simplified view of FIG. 12, the constituent members of theoxidant electrode 430 may in some embodiments be at least a partiallycombined and intermingled together. As above, in various embodiments theconductive layer 590 and/or the catalyzed active layer 600 may be of anysuitable construction or configuration, including but not limited tobeing constructed of Nickel or Nickel alloys (including Nickel-Cobalt,Nickel-Iron, Nickel-Copper (i.e. Monel), or superalloys), Copper orCopper alloys, brass, bronze, carbon, platinum, silver,silver-palladium, or any other suitable metal or alloy. In someembodiments the conductive layer 590 may comprise a current collectingscreen, while the catalyzed active layer 600 may include a catalystfilm, which in various embodiments may be formed by techniques includingbut not limited to thermal spray, plasma spray, electrodeposition, orany other particle coating method.

While in the illustrated embodiments of FIGS. 10-12 the gas vent 550 isof an air-permeable yet liquid impermeable material configuration, inother embodiments the gas vent 550 may be of any other appropriateconfiguration. For example, in some embodiments the gas vent 550 may bea pressure release nozzle configured to release gasses once a thresholdpressure is reached. In such an embodiment, a gas pocket may bemaintained at the top of the cell assembly 270, along the flow path,where the pressure release nozzle configuration of the gas vent 550 maybe configured to open to prevent an excessive buildup of gas in thepocket. In some embodiments, multiple configurations of the gas vent 550may be utilized in tandem in the cell assembly 270.

Although in the illustrated embodiments, the gas vent 550 is positionedto be on the rear sidewall for the post-cell chamber 220 (i.e. locatedon or replacing the post-cell chamber backwall space 310), in otherembodiments, the gas vent 550 may be located elsewhere along the flowpath of cell module 100. For example, instead of venting gasses througha portion of backside plate 290, the gas vent 550 may be associated withfrontside plate 280, and may vent gasses through an aperture orapertures associated with a front sidewall for the post-cell chamber220. In an embodiment, a portion of post-cell manifold 210 may comprisethe gas vent 550, or a portion of the frontside plate 280 or backsideplate 290 corresponding to post-cell manifold 210 may comprise the gasvent 550. Likewise, a top portion of the post-cell chamber 220 maycomprise the gas vent 550, such that the gasses are vented above cellmodule 100, and not through the frontside plate 280 or the backsideplate 290. In some embodiments, multiple gas vents 550 may be positionedalong the flow path of the ionically conductive medium, to strategicallyrelease gasses that are formed within the cells 105. For example, boththe frontside plate 280 and the backside plate 290 may comprise gasvents 550 to release the gasses from the cell module 100. Generally thegas vents 550 will be downstream in the flow path from the cells 105 inthe cell chamber 110, so that gasses evolved during the charging ordischarging of the cells 105 will travel with the flow of the ionicallyconductive medium until being discharged, although in an embodiment thegas vent 550 may be located alongside or below the cells 105, dependingon the configuration of the cells 105 and/or the cell module 100. In anembodiment, the gas vent 550 may be integrated into some of the seals orgaskets that prevent the ionically conductive medium from inadvertentlyleaving the cell module 100. For example, in an embodiment, the gas vent550, or one of a plurality of gas vents 550, may be positioned where thewires or other conductors that are connected to the electrodes of theelectrode assembly 410 and/or the oxidant electrode 430 exit the cellmodule 100, so that gas may additionally escape at that location, whileproviding a barrier to prevent leakage of the ionically conductivemedium.

It should be understood that other mechanisms for limiting orsuppressing unwanted gasses may be utilized in addition to gas vent 550.For example, to limit or suppress hydrogen evolution at the fuelelectrode 360, which in some cases may occur during the discharge modeor during quiescent (open circuit) periods of time, salts may be addedto retard hydrogen evolving reactions. Salts of stannous, lead, copper,mercury, indium, bismuth, or any other material having a high hydrogenoverpotential may be used. In addition, salts of tartrate, phosphate,citrate, succinate, ammonium or other hydrogen evolution suppressingadditives may be added. In an embodiment, metal fuel alloys, such asAl/Mg may be used to suppress hydrogen evolution. Additionally, otheradditives may also or alternatively be added to the ionically conductivemedium, including, but not limited to additives which enhance theelectrodeposition process of the metal fuel on the fuel electrode 360,such as is described in U.S. patent application Ser. No. 13/028,496,incorporated in its entirety by reference above. Such additives mayreduce the loose dendritic growth of fuel particles, and thus thelikelihood of such fuel particles separating from the fuel electrode360, which may reduce hydrogen evolution at the catch trays configuredto receive such particles, for example.

The embodiments of the cells 105 should not be considered to be limitingin any way and are provided as non-limiting examples of how the cell 105may be charged or discharged. U.S. patent application Ser. No.12/885,268, filed on Sep. 17, 2010, the entire content of which isincorporated above by reference, describes embodiments of a rechargeableelectrochemical cell system with charge/discharge mode switching in thecells. As also noted above, the fluid connections between multiple cells105 in the cell assemblies 270 may vary. Additional details ofembodiments of cells 105 that are connected in series are provided inU.S. patent application Ser. No. 12/631,484, filed Dec. 4, 2009 andincorporated above by reference in its entirety. Although some of thecell assemblies 270 described above have two cells 105 enclosed therein,creating a bicell, the present invention may be practiced withadditional cells 105 stacked and fluidly connected to the illustratedcells 105 of the cell assembly 270, creating tricells, quadcells, or soon. Additionally, as indicated above, in some embodiments the ionicallyconductive medium might be generally stationary within the cell module100, and might not flow. Alternative and additional mechanisms toincrease ionic resistance between fluidly connected cells may beutilized in the present invention, such as those discussed in U.S.patent application Ser. No. 12/631,484, incorporated by reference above.

The foregoing illustrated embodiments have been provided solely forillustrating the structural and functional principles of the presentinvention and are not intended to be limiting. For example, the presentinvention may be practiced using different fuels, different oxidizers,different electrolytes, and/or different overall structuralconfiguration or materials. Again, in some embodiments the configurationof the cell 105 may be similar to those disclosed in the U.S. patentapplications incorporated by reference above. Thus, the presentinvention is intended to encompass all modifications, substitutions,alterations, and equivalents within the spirit and scope of thefollowing appended claims.

What is claimed is:
 1. An electrochemical cell system comprising: one ormore electrochemical cells, each comprising: (i) a fuel electrodecomprising a metal fuel; and (ii) an oxidant electrode spaced from thefuel electrode comprising active material; a liquid ionically conductivemedium for conducting ions between the fuel and oxidant electrodes tosupport electrochemical reactions at the fuel and oxidant electrodes; ahousing configured to contain the ionically conductive medium in the oneor more electrochemical cells; a gas permeable and liquid impermeablemembrane positioned along a portion of the housing and configured toclose the portion of the housing to contain the ionically conductivemedium therein, the gas permeable and liquid impermeable membrane havingan inner surface facing the ionically conductive medium wherein theinner surface comprises a first portion and a second portion; whereinthe first portion of the gas permeable and liquid impermeable membranedoes not have the oxidant electrode active material and provides a ventfor the cell to permit gas in the housing to permeate therethrough forventing of the gas from the one or more electrochemical cells and thesecond portion of the gas permeable and liquid impermeable membrane hasthe oxidant electrode active material to comprise the oxidant electrode;and wherein the fuel electrode and the oxidant electrode are configuredto, during discharge, oxidize the metal fuel at the fuel electrode andreduce an oxidant at the oxidant electrode to generate a dischargepotential difference therebetween for application to a load.
 2. Theelectrochemical cell system of claim 1, wherein the gas permeable andliquid impermeable membrane comprises a fluoropolymer material.
 3. Theelectrochemical cell system of claim 2, wherein the fluoropolymermaterial comprises polytetrafluoroethylene.
 4. The electrochemical cellsystem of claim 1, wherein the liquid ionically conductive medium isconfigured to flow in a flow path through and among the one or moreelectrochemical cells.
 5. The electrochemical cell system of claim 4,wherein the gas permeable and liquid impermeable membrane is positioneddownstream along the flow path from the fuel electrode and the oxidantelectrode, and configured to vent by permeation gases generated duringelectrochemical reactions at the fuel and oxidant electrodes.
 6. Theelectrochemical cell system of claim 4, wherein the gas permeable andliquid impermeable membrane is configured to contact the ionicallyconductive medium while it flows through the flow path.
 7. Theelectrochemical cell system of claim 5, wherein the housing comprises acell module configured to receive the fuel electrode, and at least onesidewall configured to receive the oxidant electrode and the gaspermeable and liquid impermeable membrane, wherein the at least onesidewall is assembled onto the cell module to constrain the ionicallyconductive medium to the flow path.
 8. The electrochemical cell systemof claim 1, wherein each electrochemical cell further comprises acharging electrode selected from the group consisting of (a) the oxidantelectrode, (b) a separate charging electrode spaced from the fuel andoxidant electrodes, and (c) a portion of the fuel electrode.
 9. Theelectrochemical cell system of claim 8, wherein the fuel electrode andthe charging electrode are configured to, during re-charge, reduce areducible species of the metal fuel to electrodeposit the metal fuel onthe fuel electrode and oxidize an oxidizable species of the oxidant byapplication of a re-charge potential difference therebetween from apower source.
 10. The electrochemical cell system of claim 9, whereinthe fuel electrode comprises a series of permeable electrode bodiesarranged in spaced apart relation; wherein the spaced apart relation ofthe permeable electrode bodies enables the re-charge potentialdifference to be applied between the charging electrode and at least oneof the permeable electrode bodies, with the charging electrodefunctioning as the anode and the at least one permeable electrode bodyfunctioning as the cathode, such that the reducible fuel species arereduced and electrodeposited as the metal fuel in oxidizable form on theat least one permeable electrode body, whereby the electrodepositioncauses growth of the metal fuel among the permeable electrode bodiessuch that the electrodeposited metal fuel establishes an electricalconnection between the permeable electrode bodies.
 11. Theelectrochemical cell system of claim 9, wherein the reducible species ofthe metal fuel comprises ions of zinc, iron, aluminum, magnesium, orlithium, and wherein the metal fuel is zinc, iron, aluminum, magnesium,or lithium.
 12. The electrochemical cell system of claim 1, wherein theionically conductive medium comprises an aqueous electrolyte solution.13. The electrochemical cell system of claim 12, wherein the aqueouselectrolyte solution comprises sulfuric acid, phosphoric acid, triflicacid, nitric acid, potassium hydroxide, sodium hydroxide, sodiumchloride, potassium nitrate, or lithium chloride.
 14. Theelectrochemical cell system of claim 1, wherein each electrochemicalcell has an associated said housing.
 15. An electrochemical cell systemcomprising: a housing; one or more electrochemical cells positionedwithin the housing, each comprising: (i) a fuel electrode comprising ametal fuel; and (ii) an oxidant electrode spaced from the fuel electrodecomprising active material; a gas permeable and liquid impermeablemembrane positioned to define a portion of a surface of the housing,wherein the gas permeable and liquid impermeable membrane comprises aninner surface having a first portion and a second portion; a liquidionically conductive medium, within the housing, for conducting ionsbetween the fuel and oxidant electrodes to support electrochemicalreactions at the fuel and oxidant electrodes; wherein the fuel electrodeand the oxidant electrode are configured to, during discharge, oxidizethe metal fuel at the fuel electrode and reduce an oxidant at theoxidant electrode to generate a discharge potential differencetherebetween for application to a load; wherein the gas permeable andliquid impermeable membrane is configured to prevent permeation of theionically conductive medium out of the housing, the inner surface facingthe ionically conductive medium, and wherein the first portion of theinner surface of the gas permeable and liquid impermeable membrane doesnot have the oxidant electrode active material and provides a vent forthe cell to permit gas in the housing to permeate therethrough forventing of the gas from the one or more electrochemical cells, and thesecond portion of the gas permeable and liquid impermeable membrane hasthe oxidant electrode active material to comprise the oxidant electrode.